In vehicles employing water-cooled and pressurized-oil-lubricated internal combustion engines, inadequate oil pressure or excessively high temperature of the cooling water can cause very serious damage. The majority of engine-driven vehicles of this kind carry devices or warning lamps, indicative of the oil pressure and of the water temperature, on the instrument panel (dashboard) to warn the driver of the inadequate oil pressure or excessive high temperature. However, frequently, the attention of the driver is almost completely engaged by traffic, and an indication of inadequate oil pressure or excessively high temperature will not be noticed in time to avoid damage to the engine.